1. Field of the Invention
The invention relates to a polyaxial bone anchoring device, in particular for use in spinal or trauma surgery. The polyaxial bone anchoring device comprises a bone anchoring element with a shank to be anchored in a bone and a head. The head is pivotably held in a receiving part and can be fixed at an angle by applying pressure onto it via a pressure member. With the receiving part, the bone anchoring element can be coupled to a stabilization rod that is placed into a channel of the receiving part and that can be secured by a locking member. The pressure member comprises a deformable portion. When the locking member is advanced into the channel, first, the locking member contacts the pressure member resulting in a load applied to the pressure member that clamps the head and thereafter the locking member contacts the pressure member such that the deformable portion is deformed and the locking member comes into contact with the rod and clamps the rod. With such a locking member the head and the rod can be fixed in a sequential manner using a tool with a single drive portion that engages the locking member.
2. Description of Related Art
US 2003/0100896 A1 describes a polyaxial bone anchoring device wherein in one embodiment a single piece locking element is used to lock the head and the rod simultaneously when the locking element is tightened.
U.S. Pat. No. 7,972,364 describes a locking assembly for securing a rod in a rod receiving part of a bone anchoring device that includes a first locking element and a second locking element. With the first locking element and the second locking element the head of the bone anchoring element and the rod can be locked independently using a tool with two drive portions.
U.S. Pat. No. 8,088,152 B2 describes an orthopedic retaining system comprising at least one bone screw which has a head part and a threaded shaft pivotably mounted thereon. A clamping element is mounted in the head part, which can be pressed against the threaded shaft from its upper side and, as a result, secure the threaded shaft relative to the head part. A retaining bar is arranged in a receptacle of the head part. Further, a clamping device is provided on the upper side of the head part, by means of which the clamping element and the retaining bar are pressed into the head part such that the threaded shaft and the retaining bar are secured in positions relative to the head part. The clamping device comprises an elastically deformable pressure element which is displaced into a clamping position during actuation of the clamping device. With such a configuration, upon actuation of the clamping device, the pressure element abuts first on the clamping element and thereby secures the pivotable threaded shaft in position on the head part while the retaining bar remains freely displaceable. Only upon further actuation of the clamping device the pressure element is elastically deformed thereby abutting on the retaining bar and securing the retaining bar in position.